1. Field of the Invention
This invention relates to a disc clamper for holding a disc between a turntable and the disc clamper in a disc drive and a disc drive provided with the disc clamper.
2. Description of the Prior Art
In a disc drive such as a CD-ROM drive or a CD-R drive, for example, increase in the rotational speed of an optical disc has been attempted in recent years, and high speeds such as the 4 times speed, 8 times speed, and 12 times speed have actually been achieved.
In such a disc drive, when playing back or playing back and recording of an optical disc is carried out, the disc is placed on a turntable which is raised from down below the disc, and then the disc is rotated by being held between the turntable and a disc clamper which is provided rotatably facing the top side of the turntable.
Conventionally, in these disc drives, a disc clamper having a diameter greater than the diameter of the turntable is used in order to obtain a stabilized rotation of the disc surface by suppressing the flutter of the disc during the rotation.
However, when the rotational speed of the disc becomes high as mentioned above, the use of a disc clamper with a large diameter will cause vibrations of the disc drive owing to a slight decentering of the disc clamper and the like. Moreover, in playing back the disc, it is usual to change the rotational speed of the disc according as the playback of the inner tracks and the playback of the outer tracks of the disc. In this case, when the diameter of the disc clamper is large and its weight is large accordingly, a problem arises in that a smooth control of the rotational speed is difficult due to its high inertia.
For this reason, in such a high speed disc drive, it is said that it is desirable to set the diameter of the disc clamper to be equal to or smaller than the diameter of the turntable. It is to be noted in this connection that the diameter of the turntable is restricted to a specified value owing to the relationship to the size of the recording surface of the disc determined by the standard.
In the meantime, there still exists a request to depress the disc from above by the use of a clamper with a diameter larger than that of the turntable in order to obtain a stabilized rotation of the disc surface by suppressing the flutter during the rotation.